Xiph.org has released Theora 1.1 alpha 1. This is the first release to include the rewritten and much improved "Thusnelda" encoder. See Xiph's press release for details; this mailing list post links to binaries.

The standards like MPEG ASP, H.263/+/++, H.264 are versatile. You can adjust settings efficiently for particular bitrate. For example Xvid:Low bitrates: H.263 quantization. High bitrates: MPEG or any other custom matrix. Some particular setting for min/max quantizers, etc.

It's also applicable to use some external smart pre processing to increase compressibility. Some of them actually are very efficient.

Maybe on2 Vpx codecs can be considerated as AAC+ equivalent but it's rather to consider this situation as a lack of versatility as they're not better than MPEG versatile codecs at any bitrate. However Vpx codec also have adjustments for different bitrate but they're just more efficient for low bitrates than for high ones.